“Welcome to the Crossroads Guitar Festival,” Eric Clapton said politely, as he sat down with an acoustic guitar to kick off night one of the fourth Crossroads Guitar Festival at New York’s Madison Square Garden.

Playing a rare stripped down acoustic set, accompanied by Steve Jordan on drums and Willie Weeks on bass, he opened with Robert Johnson’s “Driftin’ Blues.” He was then joined by guitarist Doyle Bramhall II, keyboardist Chris Stainton and guitarist Andy Fairweather-Low, the latter taking lead vocals on his own song “Spider Jiving.” Clapton played rhythm guitar and sang backup for that song, which set the tone for the night: the biggest star on the bill was only too happy to play support to his friends. Clapton isn’t just the biggest star of the Crossroads Guitar Festival, he’s a genial – and most generous – host, joining lesser known artists throughout the evening. The festival, which featured guitar players ranging in age from 13 to 87, raises money for Clapton’s Crossroads substance abuse rehabilitation center in Antigua. You can learn more about the center, and donate to it, here.

Clapton didn’t just play blues songs and back up other artists: he knew that the audience paid high prices for tickets to see him play some of the songs that made him famous, and during his opening set, he obliged. A soulful rearrangement of “Tears In Heaven,” propelled by a mellow reggae backbeat, was the first of his radio hits. Vince Gill (celebrating his birthday) then joined the group for two songs that could have easily fit in on the country charts: “Lay Down Sally” and “Wonderful Tonight.” That ended Clapton’s brief set, but it wouldn’t be the last fans would see from him during the evening.

Booker T. Jones took the stage next, joined by MG’s guitarist Steve Cropper for one of their first performances together since the passing of their bandmate, Donald “Duck” Dunn. They opened with “Time Is Tight,” and launched right into “Hip Hug Her.” keb’mo later joined them for a rocking version of “Born Under A Bad Sign,” a song that Jones wrote for Albert King (King will be inducted into the Rock and Roll Hall Of Fame next week). Keb’mo, Cropper, Albert Lee, Matt “Guitar” Murphy and Blake Mills all traded leads (directed by Jones) in an amazing, but never bombastic jam. The group closed with – of course – Booker T & The MG’s timeless instrumental classic, “Green Onions.”

Robert Cray was the next act, and he was joined by a number of guests. Shortly into his set, he welcomed B.B. King for “Let The Good Times Roll” and “Sweet Sixteen.” Cray and King traded solos throughout the song, grinning at each other the whole time, as if they were having some unspoken conversation. Eric Clapton then joined for his first guest appearance of the night, along with Texas legend Jimmie Vaughan for “Every Day I Have the Blues,” with all four six stringers sitting at the front of the stage (King joked that the other three were sitting just so they wouldn’t make an old 87 year old man feel bad).

John Mayer opened his set with “Who Says,” singing “It’s been a long night in New York City,” but no one in the audience was complaining. He followed with “Slow Dancing In A Burning Room,” his voice sounding as good as it did before he damaged his vocal chords last year. While his relationships with celebrity women get him as much attention as his music, his guitar playing proves why he deserves to share a stage with the likes of Clapton, Cray and Vaughan. “Queen Of California” was next. He strategically dropped in a line from Bob Dylan’s breakup classic “If You See Her Say Hello,” probably aimed at his recent ex-girlfriend Katy Perry. Mayer was then joined by country star Keith Urban for a cover of the Beatles’ “Don’t Let Me Down.”

Buddy Guy followed; the only possible negative about having Buddy play on a multi-artist bill is that you very well may forget everyone else who took the stage before him, such is his power as a performer. In his 70s, he still is one of the greatest performers in blues, or any other genre. Joined by his 13 year old protégée Quinn Sullivan and sacred steel guitarist Robert Randolph, they nearly blew the roof off with opening number “Damn Right I’ve Got The Blues.” followed by “Let The Door Knob Hit You” and “Slippin’ In.” On the latter song, Guy had the Garden singing the lines from the song back to him, leaving fans to wonder why he hasn’t been an arena headliner for the past few decades (although his theater shows allow fans more intimacy with the legend). After leaving the stage, Randolph told Radio.com “It’s great to play with legends (like Buddy) and to be accepted by legends.” (He certainly has been more than simply “accepted”: Carlos Santana is one of the guests on his upcoming album Lickity Split). Sullivan told Radio.com that he is thankful for the many opportunities that he’s had thanks to Guy, who often takes him on tour. After leaving to catch the Allman Brothers set, many in the press room were stunned that he is such an excellent player at such a young age (bringing comparisons to Allmans guitarist Derek Trucks, who joined that band before he was old enough to drink – and after he’d already released a few solo albums).

Dan Akyroyd, the night’s MC, then put on his Elwood Blues shades and grabbed his harmonica, and accompanied by keb’mo, performed Muddy Waters’ “Got My Mojo Workin’,” noting that Waters would have turned 100 this month. And after that, he introduced the night’s final act: the Allman Brothers Band. Fresh from their annual March Madness residency uptown at New York City’s Beacon Theatre, the group started with the opening tracks from their 1969 self-titled debut, “Don’t Want You No More”/”It’s Not My Cross To Bear,” before welcoming their first guests of the evening, folk/blues legend Taj Majal and Los Lobos members Cesar Rojas and David Hildago for “Statesboro Blues,” which saw Majal playing harmonica and trading lead vocals with Gregg Allman. After “Black Hearted Woman,” came the moment that the audience was waiting for: the jam with Clapton himself.

Clapton, of course, was bandmates with the Allman’s late leader, Duane Allman, in Derek & The Dominoes. Current Allmans guitarist Derek Trucks was actually named after that album, and has done a stint in Clapton’s backing band, so it wasn’t completely unexpected that he’d join them. They played just one song – Derek & The Dominoes’ “Why Does Love Love Got To Be So Sad,” and while the crowd was surely hoping for “Layla,” anyone complaining would be churlish: it was a great moment that helped to close a great night.

The Crossroads festival continues tonight (April 13) at Madison Square Garden, Clapton will likely perform again, and other artists on the bill include Jeff Beck and former Band leader Robbie Robertson.